Transcript for 'Gangnam Style' Star Psy Apologizes for Anti-American Song

First this morning, the guy that has americans of all stripes, gallups like drunking horses. We're talking about psy, the south korean rapper behind the "gangnam style" phase. Psy engaged in vitriolic anti-american rages. Reporter: Shocking anti-american performance several years o. It comes one day before he's supposed to perform at a christmas concert, with president obama hen his family in attendance. He's the creator of the most-watched yublt video of all-time. And the dance that swept the nation, "gangnam style." Now, psy is fighting off controversy. It has to do with this. In 2004, after a korean missionary was killed in iraq, psy performed at a protest concert. Singing along to another band's song called "dear american" including these lyrics. Kill those bleeping yankees have been torturing on iraqi captive. Kill their daughters, mother daughters-in-law and brothers. If you were making up horrible things that a pop star would say that would get them in trouble, you'd have a hard time coming up with worse things than this. Reporter: It turns out psy is no stranger to controversy. After two students were killed with a u.S. Tank, he performed at a concert where he smashed a model u.S. Tank in response. For psy, it's a p.R. Nightmare, who has made millions of dollars from "gangnam style." Becoming so popular, he headlines this year's american usic awards. Made a video with heidi klum. Has appeared on "ellen," "the view," and performed for servicemen and women. Remarkable for someone whose break out video isn't even in english. Now, he's distancing himself from the controversy. Saying in a statement, the song I was featured in fromight years ago, was part of a deeply emotional reaction to the war in iraq and the killing of two korean schoolgirls that was part of the overall anti-war sentiment shared by others around the world at that time. I will forever be sorry for any pain I've caused by those words. Now, in that apology, psy points out he went to school and lived in the united states. And he understands the sacrifices american servicemen and women have made. As for tomorrow's concert, the white house confirms president obama will attend. Saying, it's not up to them who gets invited to perform. From a p.R. Perspective, it will be interesting to watch. And social media. I'm surprised it took this long to come out. It has been percolating in south korea. But it's now hitting america, big-time. Thank you very much.

This transcript has been automatically generated and may not be 100% accurate.